Inhibiting rusting of aerosol type containers



United States Patent Ofifice 3,020,122 Patented Feb. 6, 1962 The present invention relates to the prevention of rusting of aerosol type containers, and especially the caps thereof, and more particularly to a method of treating aerosol containers with a rust inhibitor whereby the tendency of the containers, and especially their caps, to rust when exposed to moisture is substantially reduced or completely eliminated. This application is a continuation-in-part of co-pending application Serial No. 596,163 filed July 6, 1956, now abandoned.

In the filling of carbon steel aerosol type containers for use as dispensers for toilet preparations the containers after being filled with the preparation under pressure are submerged in a water bath for a period of time, e.g., approximately 4 /2 minutes, at approximately 155 F. to test for leaks. The containers upon being removed from the water bath have some of the adhering Water removed by passing the containers under air jets. Although some of the adhering water is removed, the containers are by no means dry and some moisture remains on the containers which are then allowed to dry prior to packaging. During this drying period the moisture in contact with the container has a tendency to rust the container caps. Substantial rusting makes the containers unfit for commercial use.

According to the present invention it has been found that if diammonium phosphate is present in the water bath in a concentration of at least 0.1% the above testing procedure may be followed with an immersion time of at least 5 seconds. There is a correlation between time and concentration which should be observed in practice of the process of the invention. if the concentration is at the minimum level of 0.1%, the time of exposure to the water bath should be more than the minimum time of 5 seconds since some rusting has been observed where the caps were in contact with a 0.1% solution for 5 seconds whereas good protection against rusting was obtained at 0.1% concentration where the exposure time was 30 seconds and more and also where the exposure time was 5 seconds and the concentration was 0.2% and more. The maximum exposure time has not been found to be critical on rust inhibition but there is a tendency for undesired and unsightly crystalline deposits to form on the dried containers where the exposure time is about M2 hour or longer with concentrations of about 3% and with much shorter exposure times if the concentration exceeds 0.4% which is the highest permissible concentration for practicable immersion times without getting the undesired crystalline deposit.

The pH of the diammonium phosphate solutions in the concentrations from 0.1% to 0.4% falls Within the range of about 8 to 8.2; at which values, or even at a lower value of pH 7 and higher, the equipment used in the water bath treatment is not harmed by the presence of the diammonium phosphate.

If the concentration of diammonium phosphate is below 0.1%, the inhibitor will not operate at its maximum effectiveness.

Other known rust inhibitors have been tried, e.g. sodium nitrite, sodium hydroxide, sodium metasilicate, G.D. Silicate, potassium silicate, i.e., Kasil 1 and Kasil 6 produced by Philadelphia Quartz Co., tetrasodiurn polyphosphate, mercaptobenzothiazole solution, N-Silicate, C-Silicate and sodium dichromate, monoammonium dihydrogen phosphate, potassium dihydrogen phosphate and disodium hydrogen phosphate. However, they have proved unsuccessful because they are less effective as inhibitors, are harmful to the equipment employed, or result in unsightly stains on the containers.

Summarizing, the present invention is based upon a process of treating carbon steel aerosol type containers,

either plain or tin plated, with diammonium phosphate to substantially minimize or completely eliminate rusting of the containers.

While the invention has been described in terms of preferred embodiments thereof, it is to be understood that considerable variation from the details herein disclosed may be made without departing from the true scope and spirit of the invention. Accordingly, the invention is to be limited only by the claims set forth hereinafter.

What is claimed is:

1. A process for the prevention of rusting of carbon steel aerosol type containers which comprises immersing said containers in an aqueous solution containing at least 0.1% of diammonium phosphate for a sufficient period of time from 5 seconds and higher to prevent rusting on drying without leaving an undesired crystalline deposit.

2. A process for the prevention of rusting of carbon steel aerosol type containers which comprises contacting said containers for a period of at least 5 seconds with an aqueous solution containing from about 0.1% to 0.4% diammonium phosphate.

3. A process for the prevention of rusting of carbon steel aerosol type containers which comprises contacting said containers for a period of at least about 5 seconds with an essentially aqueous solution containing from about 0.1% to 0.4% diammonium phosphate at a pH of from about 7 to 8.2.

4. In a process wherein cosmetic preparations are pressure-packaged in essentially liquid phase with a liquefied normally gaseous propellant in carbon steel aerosol type containers and the thus-filled containers are tested for leaks by immersion for a period of at least 5 seconds in a hot essentially aqueous bath liquid maintained at temperatures well above room temperatures and the containers thus tested are removed from the bath and said liquid is at least superficially removed from the container surfaces, the improvement wherein subsequent rusting of the container surfaces is at least substantially minimized consisting of incorporating at least 0.1% but not over 0.4% of diammonium phosphate in said liquid and maintaining the pH thereof from about 7 to 8.2.

References Cited in the file of this patent UNITED STATES PATENTS 2,268,323 Martin Dec. 30, 1941 2,512,590 Swain June 20, 1950 2,552,874 Snyder May 15, 1951 2,872,281 Kahler et al. Feb. 3, 1959 

3. A PROCESS FOR THE PREVENTION OF RUSTING OF CARBON STEEL AEROSOL TYPE CONTAINERS WHICH COMPRISES CONTACTING SAID CONTAINERS FOR A PERIOD OF AT LEAST ABOUT 5 SECONDS WITH AN ESSENTIALLY AQUEOUS SOLUTION CONTAINING FROM ABOUT 0.1% TO 0.4% DIAMMONIUM PHOSPHATE AT A PH OF FROM ABOUT 7 TO 8.2. 